Generally, light from natural light or an artificial light source is non-polarized light (randomly polarized light), however, it is possible to take out a polarized component (linear polarized light, circular polarized light, elliptic polarized light) by utilizing a polarizing plate. Nowadays, it can be also said that a widely popularized liquid crystal display device is a device which displays images utilizing characteristics of polarized light by assembling said polarizing plate.
As a polarizing film applied for a polarizing plate, generally utilized is a light absorptive type polarizing film contain a polyvinyl alcohol type film. A polyvinyl alcohol type polarizing film is manufactured by stretching a polyvinyl alcohol type film and adsorbing iodine or dichroic dye thereon.
The transmitting axis (polarizing axis) of a polarizing film corresponds to the direction perpendicular to the stretching direction of the film. A light absorptive type polarizing film transmits only the polarized component parallel to the polarizing axis and absorbs the polarized component which is perpendicular to said axis. Therefore, utilizing efficiency of light is theoretically not more than 50% (practically a further lower value).
As a technique to depress a loss due to light absorption by a polarizing plate, known is a light utilization efficiency improvement means of a light source utilizing anisotropy in polarized light scattering in a transparent type liquid crystal display device, which is widely utilized in a brightness improving film. A polarizing film provided with anisotropy in polarized light scattering is one which utilizes a property of film prepared by stretching a complex substance of polymer and liquid crystal to form anisotropy in polarized light scattering (described in Liquid crystals, vol. 15, No. 3, pp. 395-407 (1993)), and transmits only the polarized component parallel to the polarizing axis similarly to a light absorptive type polarizing film. However, the polarizing film provided with anisotropy in polarized light scattering does not absorb the polarized component in the perpendicular direction to the polarizing axis but scatters forward or backward, resulting in improvement in a light utilization efficiency of the polarizing film.    Patent Document 1 Japanese Patent Application Publication Open to Public Inspection No. 9-274108 (hereinafter, referred to as JP-A)    Patent Document 2 JP-A No. 11-174231
Here, in patent documents 1 and 2, proposed is a method to manufacture a substance having anisotropy in polarized light scattering by blending a polymer having a positive intrinsic birefringence and a polymer having a negative intrinsic birefringence, followed by uniaxially stretching the resultant polymer.